Radar receiver display system



Jan. 26, 1954 R. P. HAVILAND 2,667,575

RADAR RECEIVER DISPLAY SYSTEM Filed March 29, 1949 Patented Jan. 26,1954 RADAR RECEIVER DISPLAY SYSTEM sec- The present invention relates toan improvement in radar receiver display systems and more particularlyto a radar receiver display system having means for improving thepresentations of beacon signals.

At the present time radar systems have two modes .of operation, onebeing search operation or the scanning of a particular area to determinethe presence, position and other characteristics of any targets in thatarea, and the other being beacon operation or the reception of signalsfrom known beacons located at known fixed points for the purpose ofindicating the position and course of the mobile craft. In these systemsthe beacon signals, which are usually coded, are received and passedthrough the same channels as the target echo signals and are often notclearly visible and distinguishable to the observer thereby reducing thevalue of such beacon signals for accurate and rapid presentation of thecrafts position.

It is an object of this invention to provide a radar receiver displaysystem having means for enhancing the presentation of beacon signals.

Another object is to provide a radar display system with means forincreasing the vsibility of beacon signals on the display device of thesystem.

A further object of this invention is the provi sion of means in a radardisplay system for increasing the brilliancy of radar beacon signals aspresented on the display device of the system.

Still another object is to provide a predetermined distortion in thereceiver of a radar system when beacon signals are being received inorder to increase the relative length and thereby the visibility of suchsignals.

A still further object of this invention is the provision of means forcontrolling at will the presentation of the beacon signals on thedisplay device of the radar receiver.

The exact nature of this invention as well as other objects andadvantages thereof will be readily apparent from consideration of thefollowing specification relat ng to the annexed drawing in which:

Fig. 1 is a wiring diagram of a conventional radar receiver seconddetector and limiting amplifier.

Fig. 2 is a wiring diagram of an improvement of Fig. 1 including oneembodiment of the present invention; and

Fig. 3 illustrates the wave forms of a typical beacon signaI at variouspoints in the circuits of Figs. 1 and 2.

Referring now to the drawings, wherein like reference charactersdesignate 1ike or corresponding parts throughout the several views,there is shown in Fig. 1 a portion of a conventional radar receivercomprising a second detector tube ll having its input connected to theincoming radio frequency signal, and having a load circuit comprising aseries inductance 2, a condenser l3 and a resistor i l. The load circuitof tube II is resistance-capacitance coupled, by means of inputcondenser l5 and grid-leak resistor Hi, to the input of a limitingamplifier tube I I having a cathode bias resistor l8 connected thereto,there being a bypass condenser I9 across resistor I8.

Under normal operation of the system of Fig. 1 for target searching, thecircuit constants are so chosen as to maintain the wave form of incomingecho signals substantially undistorted. Thus, as shown in Fig. 3, anincoming radio frequency signal 2| produces an essentially undistortedsquare wave pulse 22 at the detector output, which is then limited andamplified by tube I? to produce the wave 23 for application to thecontrol grid of the display device, not shown.

Referring now to Fig. 2, wherein is shown an improvement of the circuitof Fig. 1 according to the present invention, a resistor 24 is insertedbetween one end of resistor l4 and ground, and a resistor 25 isconnected between the cathode end of resistor I8 and one fixed contact26 of relay 21, the other fixed contact 28 of relay 2'! being connectedto the junction point of resistors M, 2 8, while the movable contact 29is grounded. Under normal search operation of the circuit of Fig. 2,relay 2! remains deenergized so that mov- 1 able contact 29 is connectedto fixed contact 28 and resistor 24 is thereby shorted. Resistor 25,under these conditions, is not in the circuit and the operation isidentical with that of the circuit of Fig. 1.

When beacon operation is desired, relay 2! is energized therebyconnecting contacts 26 and 29 so that resistor 24 is in series withresistor l4 and resistor 25 is shunted across resistor Hi. In thismanner the time-constant of the discharge path of the detector circuitis increased so as to provide a distortion of the incoming signal 2 la,as shown in Fig. 3, thereby efiectively increasing the time duration ofthe signal 22a at the output of the detector circuit. Similarly, byconnecting resistor 25 in parallel with resistor IS, the self biasing oftube H is decreased thereby increasing the gain and limiting level oftube I! so that the output 23a. of tube l7, and the relative brillianceof the beacon signals on the display device, is increased.

ing the predetermined distortion into the circuit so as to increase therelative length of thebeacon signals. It is, therefore, to be understoodthat, within the scope of the appended claims, the invention may bepracticed otherwise than as specifically described.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

What is claimed is:

1, In a radar receiver, a limiting amplifier, tube having a plate, agrid and a cathode; a detector tube, an inductance and a first condenserconnected in series and coupled to the grid of said limiting amplifiertube; a second condenser one side of which is connected to ground andthe otherside between the detector tube and the inductance; a firstresistor, a second resistor, one end ofthe first resistor beingconnected between the inductance and first condenser and the other endbeing connected to the second resistor, the latters opposite end beingconnected to ground; athird resistor oneend. of which isconnectedbetween the first condenser and the grid of the, limiiting amplifi ertube and the other end of which isconnected to ground; agfou'rthresistor, one end.

of which is connected to the cathode of the limi5 iting amplifier tubeand the other end of which is connected to ground; a third condenserconnected in parallel with the fourth resistor; a fifth resistor, oneend of which is connected to said cathode; and a relay switch having amovable contact connected to ground, and having first and second.fixed.contacts,,.said first contact being connected between, said firstand secondresistors, said second contact being connected to the otherend of said fifth resistor.

2. In a radar receiver including a triode amplifier having a plate, agrid and a cathode, a firstv self biasing resistor connected in thecathode circuit of said triode: a diode detector having a chargingcircuit in its output, and having first and second series connecteddischarge resistors connected across said charging circuit; means acoupling said first and second discharge resistors to .said grid; asecond self biasing resistor adapted for connection across said firstself biasing resistor; and switch .meansnormally short circuit-- ingsaidfirst. discharge resistor movable to simula taneously open said.short, circuit and tocorinect said second biasing resistor across saidfirst bias in resistor.

ROBERT P. HAVILAND.

References Cited in the m r t i page" UNITED STATES PA'IENTS

